import java.util.ArrayDeque;
import java.util.Deque;
import java.util.LinkedList;
import java.util.Queue;

public class Likou_lainxi1122 {


    public class queue_l {
        public static void main(String[] args) {
            Queue<Integer> q = new LinkedList<>();
            Deque<Integer> d1 = new ArrayDeque<>();
            Deque<Integer> d2 = new LinkedList<>();
            q.offer(1);
            q.offer(2);
            q.offer(3);
            q.offer(4);
            q.offer(5);
            System.out.println(q.size());
            System.out.println(q.peek());

            q.poll();
            System.out.println(q.poll()); // 从队头出队列，并将删除的元素返回

            if(q.isEmpty()){
                System.out.println("队列空");
            }else{
                System.out.println(q.size());
            }
        }
    }

}
